In many extensions the first thing is to obtain the object View and from that to obtain the associated MapControl and MapContext. This is usually the entry point. With the MapContext we have already the list of layers (Flayers), search tool for the layer that we would like to work with, etc. Let’s take a look at an example:

com.iver.andami.ui.mdiManager.IWindow view = PluginServices.getMDIManager().getActiveWindow();
if (!(view instanceof View))
    return;
View vista=(View)view;
IProjectView model = vista.getModel();
MapContext mapa = model.getMapContext();
MapControl mapCtrl = vista.getMapControl();
logger.debug("Comand : " + s);

if (s.equals("FULL") ) {
    try {
        // mapa.beginAtomicEvent();
        mapa.getViewPort().setExtent(mapa.getLayers().getFullExtent());
        mapa.clearAllCachingImageDrawnLayers();
        vista.repaintMap();
        // mapa.endAtomicEvent();
    } catch (DriverException e) {
        NotificationManager.addError("Error getting full extent",
            e);
    }
} 

This portion of code comes from the com.iver.cit.gvsig.ViewControls class. It uses PluginServices.getActiveWindow() to obtain the active window. If that window is of type View, then it gets the MapContext to show a zoom of all the layers:

mapa.getViewPort().setExtent(mapa.getLayers().getFullExtent());

The most interesting classes to review to see examples of this type are:

• ViewControls.- They are many commands in only one class: full extent, panning, configure locator map, zoom in, zoom out, meassure, set layers as visible, not visible, active, not active, save to raster, change scale...
• ViewSelectionControls.- Select by point, by rectangle, by polygon, by layer and invert selection.
• Export.- Exports to raster what is visible in a view.
• AddLayer.- It is used for adding layers to a view. It is far more complex of what it looks like, since it shows a dialog box extensible from external pluggings. In fact, it is used by other pluggings to add layers based on spatial databases, WMS, WFS, etc. In this class there is only the necessary to add layers based on files (.shp, raster, .dxf, .dgn, etc). It is also important that you pay attention to the projection treatment associated to the layer and the view. If they do not coincide, it will try to reproject on the fly.
• InfoToolExtension.- The window to show information is far more complex of what it looks like (perhaps far more than necessary). This class is only the entry point to find out its functioning.

Within the views it is very interesting to see the relationship between the MapOverview and the MapControl. We will see it next.